import React from 'react'
import ReactDOM from 'react-dom'

class Myheader extends React.Component {
  state = {
    msg: 'hello world',
  }
  render() {
    return (
      <header>
        <h1>页面头部</h1>
        <h1>{this.state.msg}</h1>
      </header>
    )
  }
}
const aa = new Myheader()
console.log(aa)

const App = () => (
  <>
    <Myheader />
    <div>内容主题</div>
    <Myheader />
  </>
)
ReactDOM.render(<App />, document.getElementById('root'))
